Sitting on my back porch in the shade, it is very readable at 100% brightness. I use transition glasses and glare is further reduced. Strange that shaded glasses (transitions do not go real dark like regular sunglasses) does not reduce perceived brightness. Anyway, you still get some glare but it's not the obtrusive kind. In direct sun it is very dim and I cannot recommend its use there.
That said, all this is subjective so there is no way to tell what you might find acceptable or not.